1 /* $NetBSD: pure_calc.y,v 1.1.1.1 2010/12/23 23:36:27 christos Exp $ */ 2 3 %{ 4 # include <stdio.h> 5 # include <ctype.h> 6 7 int regs[26]; 8 int base; 9 10 %} 11 12 %start list 13 14 %token DIGIT LETTER 15 16 %left '|' 17 %left '&' 18 %left '+' '-' 19 %left '*' '/' '%' 20 %left UMINUS /* supplies precedence for unary minus */ 21 22 %% /* beginning of rules section */ 23 24 list : /* empty */ 25 | list stat '\n' 26 | list error '\n' 27 { yyerrok ; } 28 ; 29 30 stat : expr 31 { printf("%d\n",$1);} 32 | LETTER '=' expr 33 { regs[$1] = $3; } 34 ; 35 36 expr : '(' expr ')' 37 { $$ = $2; } 38 | expr '+' expr 39 { $$ = $1 + $3; } 40 | expr '-' expr 41 { $$ = $1 - $3; } 42 | expr '*' expr 43 { $$ = $1 * $3; } 44 | expr '/' expr 45 { $$ = $1 / $3; } 46 | expr '%' expr 47 { $$ = $1 % $3; } 48 | expr '&' expr 49 { $$ = $1 & $3; } 50 | expr '|' expr 51 { $$ = $1 | $3; } 52 | '-' expr %prec UMINUS 53 { $$ = - $2; } 54 | LETTER 55 { $$ = regs[$1]; } 56 | number 57 ; 58 59 number: DIGIT 60 { $$ = $1; base = ($1==0) ? 8 : 10; } 61 | number DIGIT 62 { $$ = base * $1 + $2; } 63 ; 64 65 %% /* start of programs */ 66 67 int 68 main (void) 69 { 70 while(!feof(stdin)) { 71 yyparse(); 72 } 73 return 0; 74 } 75 76 static void 77 yyerror(const char *s) 78 { 79 fprintf(stderr, "%s\n", s); 80 } 81 82 int 83 yylex(YYSTYPE *value) 84 { 85 /* lexical analysis routine */ 86 /* returns LETTER for a lower case letter, yylval = 0 through 25 */ 87 /* return DIGIT for a digit, yylval = 0 through 9 */ 88 /* all other characters are returned immediately */ 89 90 int c; 91 92 while( (c=getchar()) == ' ' ) { /* skip blanks */ } 93 94 /* c is now nonblank */ 95 96 if( islower( c )) { 97 *value = c - 'a'; 98 return ( LETTER ); 99 } 100 if( isdigit( c )) { 101 *value = c - '0'; 102 return ( DIGIT ); 103 } 104 return( c ); 105 } 106